*waṣil- - joint, articulation (of the humerus)
(SED I No. 289)
As a nominal root with anatomic meaning, C. Sem. only.
Traditionally regarded (for example, in HALOT 82) as deverbal of Sem. *ˀ/wṣl ; the connection is quite plausible. For this verbal root see DRS 593.
Contra AHw. 28 and HALOT 431, there is probably no relationship between this root and Akk. akāṣu ‘hartnäckig sein’, akṣu ‘dangerous, overbearing, terrible’